PSA: Even if you'll still get your Tier rewards, it's not a good idea to not care if you lose Ranked

If you're, let's say Gold 2, since it's the end of the season you might feel it's ok to play suboptimally and possibly lose until you're Gold 4 or 5 because you'll still get your Victorious skin and border/icon rewards.

Sure, that is true, but you're going to tank your hidden MMR. That is going to not only make you play with less "skilled" allies and opponents, but it's going to make your placements for next season worse; we all lose around 2 divisions worth of MMR with the soft reset, so you could get placed in a lower Tier.

You don't want to have to do Tier promo matches again and have a more difficult time getting to the same spot you were before, do you? If you don't tank your MMR you can even get placed in the same division or higher.